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Abstract

Adaptive optics (AO) ophthalmoscopes with small fields of view have limited clinical utility. We propose to address this problem in reflective instruments by incorporating a viewfinder pupil relay designed by considering pupil and image centering and conjugation. Diverting light from an existing pupil optical relay to the viewfinder relay allows switching field of view size. Design methods that meet all four centering and conjugation conditions using either a single concave mirror or with two concave mirrors forming an off-axis afocal telescope are presented. Two different methods for calculating the focal length and orientation of the concave mirrors in the afocal viewfinder relay are introduced. Finally, a 2.2 × viewfinder mode is demonstrated in an AO scanning light ophthalmoscope.

Figures (5)

Pupil relay formed by a single concave mirror with focal length f. The mirror is a distance a from the entrance pupil, while the exit pupil is at a distance a f / (a - f). P0 and Pf are the initial and final vergences of the imaging beam.

AOSLO diagram [17], illustrating how the change between the high-magnification and viewfinder mode was implemented. In the later, a spherical mirror (sph 6’) and a fold mirror are positioned using magnetic mounts. This arrangement bypasses the afocal telescope formed by spherical mirror 5 and 6.

AOSLO and fundus images of subjects JC_0832 (A-E) and JC_0007 (F-J). The left and central columns show 1.75° and 2.2 × 1.75° (viewfinder mode) FOV AOSLO images, respectively, of the fovea and the optic disc. The retinal location and extent of the AOSLO images are indicated on the fundus images (right) through the red contours. All scale bars are 1° across.